1. Field of the Invention
This invention relates to a process of manufacturing a magnetic head used for a magnetic recording and reproduction apparatus such as a VCR.
2. Description of the Prior Art
With recently increasing demands for a higher recording density and a higher definition of picture quality, magnetic heads using high-saturation magnetic flux density metals, such as Permalloy, Sendust, and amorphous alloys have been highlighted in addition to the conventional ferrite materials used for magnetic head cores. Among them, amorphous alloys are excellent in terms of corrosion resistance, wear resistance, and other properties and thus are particularly promising materials for high-performance magnetic heads.
FIG. 2 is an oblique view of a head using an amorphous alloy; the head core consists of an amorphous alloy 1 sandwiched between non-magnetic substrates 2. A pair of core halves are connected across a gap forming surface 3 with a fused low-melting point glass 4. The amorphous alloy 1 is sandwiched between the non-magnetic substrates 2 by means of a low-melting point crystallization glass 5, and an anti-diffusion film 6 of SiO.sub.2 is inserted between the amorphous alloy 1 and the low-melting point crystallization glass 5 to prevent reaction between the amorphous alloy and the low-melting point crystallization glass.
FIGS. 3(a)-3(c) are oblique views showing a conventional process of manufacturing a magnetic core which uses an amorphous alloy. First, an amorphous alloy 1 is formed by sputtering on one side of a non-magnetic substrate 2, and an anti-diffusion film 6 of SiO.sub.2 is then formed by sputtering on the amorphous alloy (FIG. 3(a)). Next, a low-melting point crystallization glass film 5 is formed by sputtering on the anti-diffusion film 6 (FIG. 3(b)). Then, a number of the above substrates are laminated in layers and heat-treated under pressure to form a laminate (FIG. 3(c)). This laminate is finally processed (such as by cutting, grinding, and heat-treating it) into a finished magnetic head. In general, an amorphous alloy has a crystallization temperature and, if heat-treated at a temperature above this temperature, turns from an amorphous to a crystalline state to become magnetically less powerful. Due to the requirement for glass bonding and any other heat treatment to be carried out at a temperature lower than such a crystallization temperature, low-melting point glass whose softening point is lower than the crystallization temperature of an amorphous ally is generally used for bonding to an amorphous alloy magnetic head core. Normally, low-melting point glass is poor in mechanical strength and can hardly withstand the processing to manufacture a magnetic head. For this reason, the glass used to bond an amorphous alloy 1 and a non-magnetic substrate 2 is low-melting point crystallization glass which is mechanically strong with its softening point increasing after crystallization.
A great problem in practical use has, however, been that an amorphous magnetic head prepared by the above conventional process of manufacturing a magnetic head has many voids at the bonding interface between the non-magnetic substrate 2 and the low-melting point crystallization glass 5 as shown in FIG. 4 and the actual use of such a magnetic head in a deck deteriorates the properties of the head due to the tape shavings deposited within the voids developed at the bonding interface. Weak bonding between the non-magnetic substrate and the amorphous alloy due to the influence of voids and the resulting poor yield rate in the manufacture of magnetic heads have been another problem.